The present invention relates to a receiving device for obtaining received data by receiving a signal that is modulated by phase shift keying. In particular, the present invention relates to a receiving device for obtaining received data by receiving an OFDM symbol that is modulated by phase shift keying in power line communication through a power line.
There has been developed a technology for power line communication through a power line as a communication medium. In the next-generation power line communication, Orthogonal Frequency Division Multiplexing (OFDM) has been discussed as the main transmission scheme in terms of high-speed communication, noise immunity, frequency usage efficiency and the like.
Japanese Unexamined Patent Publication No. 2002-111626 discloses a receiving device having good decoding characteristics while reducing the amount of calculation required for decoding in a digital radio communication system using the OFDM transmission scheme. The receiving device normalizes each subcarrier signal by a preamble which is a known signal. Then, the receiving device weights the signal that is decoded from the constellation by using the received power of the subcarrier corresponding to the particular preamble. Here, the receiving device reduces the quantized bit by rounding the weighted signal based on the power average of all the subcarriers of the preamble.
With this configuration, it is possible to select a bit that contributes to Viterbi decoding more effectively than selecting an effective bit simply by cutting the lower bit off of the weighted signal. As a result, it is possible to maintain high decoding performance.
Japanese Unexamined Patent Publication No. 2008-131364 discloses a receiving device that prevents the reduction in the Viterbi decoding accuracy when interference occurs in the desired wave in a digital radio communication system using the OFDM transmission scheme. The receiving device obtains the variation from a reference symbol point of the received signal. When the variation is greater than a predetermined reference value, the receiving device determines that interference with the desired wave occurs, and corrects the soft decision value so that the contribution to decoding is reduced.
With this configuration, if the received power difference between the desired wave and the interference wave is small, the soft decision value is corrected by detecting the interference occurred in the desired wave. Thus, it is possible to prevent the reduction in the Viterbi decoding accuracy and increase the communication quality.